50% Push the Limit increases the skill MH% and OH% (Mainhand and Offhand % base values such as 750% MH meteor) by 50%.
For example I have 750% meteor. With 50% Push the Limit: 750%×1.5= 1125% MH. That can make a huge difference in DMG as you can deal more damage at the start before multiplication from Sets, Affixes, Crits, Mythics and even Deadly Strikes.
Push the Limit works like the Identity Set but the difference is that it works on any class skill and the only cost is actually making your skill casting by mana 50% more expensive. It's almost a must have set, even in some PvP builds.
If you use Both PTL and ED%:
Also ED% increases the WD% and BWD by multiplication so if you have 300%, the BWD and WD% is increased by 300%. Then that gets casted by the skill that was buffed by Push the Limit and that's before any other Multiplication such as Glasscannon, Crits, Mythics and Sets.
Inserts Why Not Both? meme.